French Pat. No. 7,318,733 discloses and claims a process for preparing 3-substituted-1-methyl-6-substituted amino-s-triazine-2,4(1H,3H) diones by a reaction sequence which includes the step of contacting an alkoxycarbonylcyanamide with an alkylating agent to form an N-alkoxycarbonyl-N-alkylcyanamide as an intermediate. In particular, the sodium salt of ethoxycarbonyl cyanamide in aqueous solution can be reacted with dimethyl sulfate (DMS) to obtain N-ethoxycarbonyl-N-methylcyanamide. As the desired reaction proceeds, the DMS also reacts with sodium chloride which is present in the original aqueous solution to form methyl chloride as an undesirable by-product. Because of the methyl chloride formation, which consumes a significant amount of DMS, a 50% excess of DMS must be added to obtain an 81% batch yield of N-ethoxycarbonyl-N-methylcyanamide. Also described is a continuous, counter-current reaction process which provides improved yields and requires a smaller excess of DMS.
Slotta and Tschesche, Ber., 62, 1393 (1929) obtained a 58% yield when the sodium salt of ethoxycarbonylcyanamide was reacted with a 60% excess of DMS. No sodium chloride was present in the experiment.
Jones, Aldrichimia Acta, Vol. 9, No. 3, pp. 35-45 (1976) describes the application of phase transfer catalysis in organic synthesis. None of the references, however, suggest the desirability of employing a catalyst in the intermediate methylation step of the reaction sequence followed for preparing 3-substituted-1-methyl-6-substituted amino-s-triazine-2,4(1H,3H) diones.